Field of the Invention
The present invention relates to a display device, and more particularly, to a three-dimensional (3D) image display device for displaying a three-dimensional stereoscopic image.
Discussion of the Related Art
A three-dimensional (3D) image display device (i.e., a stereoscopic image display device) displays a 3D image using a stereoscopic technique or an autostereoscopic technique.
The stereoscopic technique, which uses a parallax image of left and right eyes of a user with a high stereoscopic effect, includes a glass method and a non-glass method both of which have been put to practical use. In the glass method, a left and right parallax image is displayed on a direct view-based display device by changing a polarization direction of the left and right parallax image, and a stereoscopic image is implemented using polarized glasses. In the non-glass method, an optical plate, such as a parallax barrier or the like, for separating an optical axis of the left and right parallax image is installed in front of or behind a display screen.
As shown in FIG. 1, the glass method may employ a patterned retarder 3 for converting polarization characteristics of light incident on the polarization glasses (not shown) on a display panel 2. In the glass method, a left eye image and a right eye image are alternately displayed on the display panel 2, and the polarization characteristics of light incident on the polarized glasses are converted by the patterned retarder 3. Through this operation, the glass method implements a 3D image by spatially dividing the left eye image and the right eye image. In FIG. 1, a backlight unit 1 irradiates light to the display panel 2.
As shown in FIG. 2, the display panel 2 includes an upper substrate 2A and a lower substrate 2B. A polarization film (POL) is attached to an upper surface of the upper substrate 2A that on a die does not face the lower substrate 2B. Another polarization film POL is attached to a lower surface of the lower substrate 2B on a side that does not face the upper substrate 2A. The patterned retarder 3 is attached on the polarization film POL of the upper substrate 2A. The display panel 2 to which the patterned retarder 3 is attached is mounted at a stepped inner wall of a panel guide 4 made of a non-conductive material. The backlight unit 1 is received in a bottom cover 5 made of a metal material and disposed under the display panel 2. A top case 6 is made of a metal material and covers an upper edge of the patterned retarder 3, upper and side surfaces of the panel guide 4, and a side surface of the bottom cover 5. The panel guide 4, the bottom cover 5, and the top case 6 are fastened by a screw 8 that penetrates them.
An electrostatic discharge (ESD) conductive tape 7 is attached to an upper surface of the upper substrate 2A on a side that does not face the lower substrate 2B to externally discharge static electricity generated from the display panel 2. The conductive tape 7 is attached to an ESD transparent conductive film (not shown) formed on the upper surface of the upper substrate 2A and then extends so as to be attached to the upper and side surfaces of the panel guide 4 and to the side surface of the bottom cover 5. Static electricity generated from the display panel 2 is transferred to the bottom cover 5 through the conductive tape 7, and then externally discharged through the screw 8 and the top case 6. However, the 3D display device has the following problems.
First, the ESD structure of the related art 3D image display device cannot flexibly cope with a repair process. If the display panel or the backlight unit is found to be defective, the display panel or the backlight unit is separated after assembly of the 3D image display device is completed, and a repair process is performed on the separated display panel or the backlight. In this case, to separate the display panel or the backlight unit, the conductive tape must be detached from the panel guide and the bottom cover. After the repair process is performed, a conductive force of the conductive tape is drastically degraded as compared with the state before the repair process. That is, if the conductive tape is detached and then reattached, its adhesive power is much degraded as compared with its adhesive power before being detached. In addition, because the attachment portions of the conductive tape and the display panel are covered by the patterned retarder, it is not possible to replace only the conductive tape. That is, the need to remove the patterned retarder prevents replacement of the conductive tape without damaging the display panel. The weakened conductive power of the conductive tape after the repair process degrades the ability to ground the ESD.
Second, the ESD structure of the related art 3D image display device should necessarily perform the assembling process of extending the conductive tape and attaching it to the upper and side surfaces of the panel guide and the side surface of the bottom cover, a process TACT time (total average cycle time) is lengthened, and thus, an assembly efficiency is lowered. In addition, static electricity generated from the display panel is externally discharged through the conductive tape, the bottom cover, the screw, and the top case, so the discharge path is very long, which inevitably degrades discharge efficiency.